From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 13931C433DB for ; Wed, 23 Dec 2020 13:19:39 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 960D02222A for ; Wed, 23 Dec 2020 13:19:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 960D02222A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.58347.102490 (Exim 4.92) (envelope-from ) id 1ks434-0004Nv-3f; Wed, 23 Dec 2020 13:19:26 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 58347.102490; Wed, 23 Dec 2020 13:19:26 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ks434-0004No-0a; Wed, 23 Dec 2020 13:19:26 +0000 Received: by outflank-mailman (input) for mailman id 58347; Wed, 23 Dec 2020 13:19:24 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ks432-0004Nj-MI for xen-devel@lists.xenproject.org; Wed, 23 Dec 2020 13:19:24 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1ks431-000730-Pl; Wed, 23 Dec 2020 13:19:23 +0000 Received: from [54.239.6.185] (helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1ks431-0003h1-Gn; Wed, 23 Dec 2020 13:19:23 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=NbuIBhzl6Jps3KIZ/CV2Pa4RdvA7DGpXZ61NF6uZcXU=; b=w2fgR9nfYJ10HT4wULOxHJKpdk Z1sW3LTDC32SWeD+fLMkxPbgFBmRjVxdq4hPfq+EFm9bxIF0Bno+k1Z1uagylE+2gWuTCzHlDrqfz nd+jzylawlD5ZgSP0V0YGv0r6K+QuS75WskU2NZV395wvAdKwIOSuGT5wYhM50jWOqfY=; Subject: Re: [PATCH v3 4/5] evtchn: convert domain event lock to an r/w one To: Jan Beulich Cc: Andrew Cooper , George Dunlap , Ian Jackson , Wei Liu , Stefano Stabellini , "xen-devel@lists.xenproject.org" References: <9d7a052a-6222-80ff-cbf1-612d4ca50c2a@suse.com> <074be931-54b0-1b0f-72d8-5bd577884814@xen.org> <6e34fd25-14a2-f655-b019-aca94ce086c8@suse.com> <55dc24b4-88c6-1b22-411e-267231632377@xen.org> <1f3571eb-5aec-e76e-0b61-2602356fb436@xen.org> <099b99bc-c544-0aa8-c3b4-4871ef618e4a@suse.com> From: Julien Grall Message-ID: <25585b2a-7dcd-1b46-b360-9a9e9d54b191@xen.org> Date: Wed, 23 Dec 2020 13:19:21 +0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit On 23/12/2020 12:57, Jan Beulich wrote: > On 23.12.2020 12:22, Julien Grall wrote: >>> 1) Neither evtchn_status() nor domain_dump_evtchn_info() appear to >>> have a real need to acquire the per-domain lock. They could as well >>> acquire the per-channel ones. (In the latter case this will then >>> also allow inserting the so far missing process_pending_softirqs() >>> call; it shouldn't be made with a lock held.) >> I agree that evtchn_status() doesn't need to acquire the per-domain >> lock. I am not entirely sure about domain_dump_evtchn_info() because >> AFAICT the PIRQ tree (used by domain_pirq_to_irq()) is protected with >> d->event_lock. > > It is, but calling it without the lock just to display the IRQ > is not a problem afaict. How so? Is the radix tree lookup safe against concurrent radix tree insertion/deletion? Cheers, -- Julien Grall